Image mosaicing responsive to camera ego motion

Abstract

A method of generating a mosaic from a plurality of camera images of a scene acquired by a camera moving relative to the scene, the method comprising: associating with each camera image a value of at least one variable so that the variable is a substantially a linear function of a spatial coordinate that defines the locations of the camera at which it acquires the images by requiring that a coordinate of pixels in the camera images that image a same feature in the scene is substantially a linear function of the variable; and generating the mosaic responsive to the at least one variable.

1 . A method of generating a mosaic from a plurality of camera images of a scene acquired by a camera moving relative to the scene, the method comprising: 
 associating with each camera image a value of at least one variable so that the variable is a substantially a linear function of a spatial coordinate that defines the locations of the camera at which it acquires the images by requiring that a coordinate of pixels in the camera images that image a same feature in the scene is substantially a linear function of the variable; and    generating the mosaic responsive to the at least one variable.    
   
   
       2 . A method according to  claim 1  wherein the at least one variable is a single variable.  
   
   
       3 . A method according to  claim 2  wherein the camera moves along a straight line and the spatial coordinate determines displacement of the camera along the line.  
   
   
       4 . A method according to  claim 2  wherein the camera moves along an arc of a circle and the spatial coordinate is an angle that determines location of the camera among the arc.  
   
   
       5 . A method according to  claim 2  wherein the camera moves in a plane and the spatial coordinate is a coordinate that determines the location of the camera along an axis in the plane.  
   
   
       6 . A method according to  claim 2  wherein the camera moves on the surface of a sphere and the spatial coordinate is an angle that determines the location of the camera on the surface relative to a direction of an axis through the center of the sphere.  
   
   
       7 . A method according to  claim 1  wherein the variable is a time coordinate along a time axis of a space-time (ST) volume defined by the images.  
   
   
       8 . A method according to  claim 7  wherein associating values of the time coordinate comprises associating the values by requiring that at least one trajectory in an epipolar (EP) plane of the ST volume defined by pixels that image a same feature in the scene is substantially a straight line.  
   
   
       9 . A method according to  claim 8  wherein associating the values of the time coordinate comprises determining the values so that they optimize at least one global measure responsive to coordinates of the pixels in the EP plane that has a value indicative of an extent to which EP trajectories in the EP planes are straight lines.  
   
   
       10 . A method according to  claim 9  wherein the global measure comprises the entropy of at least one transform.  
   
   
       11 . A method according to  claim 10  wherein the at least one transform comprises a Fourier transform.  
   
   
       12 . A method according to  claim 10  wherein the at least one transform comprises a Radon transform.  
   
   
       13 . A method according to  claim 8  wherein associating the values of the time coordinate comprises determining the values using an iterative procedure.  
   
   
       14 . A method according to  claim 13  wherein using an iterative procedure comprises associating a time coordinate value for each camera image in turn responsive to time coordinate values already determined for other camera images.  
   
   
       15 . A method according to  claim 8  wherein associating the values of the time coordinate comprises visually spacing the camera images along the time axis so that the at least one trajectory is substantially a straight line.  
   
   
       16 . A method according to  claim 7  wherein generating the mosaic comprises generating an image of a mosaic plane of the ST volume, which image of the mosaic plane comprises pixels in the camera images that lie along mosaic lines, which are lines of intersection of the mosaic plane with the camera images.  
   
   
       17 . A method according to  claim 16  and comprising generating values for pixels in the mosaic plane at locations between mosaic lines responsive to the associated time coordinates.  
   
   
       18 . A method according to  claim 16  wherein generating the mosaic comprises defining a mosaic strip for each camera image in the ST volume that comprises the mosaic line in the camera image and juxtaposing the mosaic strips contiguous with each other to generate the mosaic.  
   
   
       19 . A method according to  claim 18  and comprising determining a width for the mosaic strip of a given camera image in the ST proportional to differences between the time coordinate assigned the given camera image and the time coordinates assigned adjacent camera images in the ST volume.  
   
   
       20 . A method according to  claim 19  and comprising determining the width of the strip responsive to a distance of a feature in the scene that is imaged in the strip.  
   
   
       21 . A method according to  claim 1  wherein, two spatial coordinates define the camera position and the at least one variable comprises two variables.  
   
   
       22 . A method according to  claim 21 , wherein each variable is a linear function of a different spatial coordinate.  
   
   
       23 . A method according to  claim 21  wherein the camera moves in a plane and the different coordinates comprise two coordinates that define the location of the camera in the plane.  
   
   
       24 . A method according to  claim 21  wherein the camera moves on a region of a spherical surface and the different spatial coordinates comprise two angles that define the location of the camera on the region.  
   
   
       25 . A method according to  claim 21  wherein associating with each camera image values of the two variables comprises associating the values so that each of two coordinates of pixels in the camera images that image a same feature in the scene is a linear function of at least one of the variables.  
   
   
       26 . A method according to  claim 25  wherein each pixel coordinate is a linear function of a different one of the variables.  
   
   
       27 . A method according to  claim 1  wherein the optic axis of the camera is substantially perpendicular to the locus of its motion or the camera images are rectified to correspond to camera images acquired with the camera optic axis perpendicular to its locus of motion.  
   
   
       28 . A method according to  claim 27  and the mosaic corresponds to an image of the scene oriented at a 0° azimuth angle relative to the optic axis of the camera.  
   
   
       29 . A method according to  claim 27  wherein the mosaic corresponds to an image of the scene oriented at an azimuth angle other than 0° relative to the optic axis of the camera.  
   
   
       30 . A method according to  claim 27  wherein the mosaic comprises pixels that image features in the scene at different azimuth angles relative to the optic axis of the camera.  
   
   
       31 . A method according to  claim 21  wherein the optic axis of the camera is substantially perpendicular to the locus of its motion or the camera images are rectified to correspond to camera images acquired with the camera optic axis perpendicular to its locus of motion.  
   
   
       32 . A method according to  claim 31  and the mosaic corresponds to an image of the scene oriented at a 0° azimuth angle relative to the optic axis of the camera.  
   
   
       33 . A method according to  claim 31  wherein the mosaic corresponds to an image of the scene oriented at an azimuth angle other than 0° relative to the optic axis of the camera.  
   
   
       34 . A method according to  claim 31  wherein the mosaic comprises pixels that image features in the scene at different azimuth angles relative to the optic axis of the camera.